In the prior art, it is common to have a dial type combination lock consisting of a combination of several locking discs each of which has a groove for the locking bolt and which must be controlled separately one by one by rotation of a single dial of the lock. In other words, in ordinary safe locks having a four locking disc system, in order to open the lock, the dial must be turned four times in one direction, three times in the other direction, two times in the one direction, and one time in the other direction, respectively. When the user makes a mistake during the rotation of the dial, he must repeat the rotations of the dial from the beginning. Thus, in order to make the numbers for each of the lock discs coincide with the designated numbers during the rotation of the dial, the user must spend considerable time and may become nervous.